# Lesson Learned

Analyze recent code changes via git history and extract software engineering lessons.

- Repository: https://github.com/softaworks/agent-toolkit (2611 stars)
- Category: Git and review
- License: MIT
- Last updated: 2026-03-05
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add softaworks/agent-toolkit --skill lesson-learned -g -a claude-code -y`
Codex: `npx skills add softaworks/agent-toolkit --skill lesson-learned -g -a codex -y`
Cursor: `npx skills add softaworks/agent-toolkit --skill lesson-learned -g -a cursor -y`
Gemini CLI: `npx skills add softaworks/agent-toolkit --skill lesson-learned -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add softaworks/agent-toolkit`

## Description

Analyze recent code changes via git history and extract software engineering lessons. Use when the user asks 'what is the lesson here?', 'what can I learn from this?', 'engineering takeaway', 'what did I just learn?', 'reflect on this code', or wants to extract principles from recent work.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Lesson Learned

Extract specific, grounded software engineering lessons from actual code changes. Not a lecture -- a mirror. Show the user what their code already demonstrates.

## Before You Begin

**Load the principles reference first.**

1. Read `references/se-principles.md` to have the principle catalog available
2. Optionally read `references/anti-patterns.md` if you suspect the changes include areas for improvement
3. Determine the scope of analysis (see Phase 1)

**Do not proceed until you've loaded at least `se-principles.md`.**

## Phase 1: Determine Scope

Ask the user or infer from context what to analyze.

| Scope | Git Commands | When to Use |
|-------|-------------|-------------|
| Feature branch | `git log main..HEAD --oneline` + `git diff main...HEAD` | User is on a non-main branch (default) |
| Last N commits | `git log --oneline -N` + `git diff HEAD~N..HEAD` | User specifies a range, or on main (default N=5) |
| Specific commit | `git show <sha>` | User references a specific commit |
| Working changes | `git diff` + `git diff --cached` | User says "what about these changes?" before committing |

**Default behavior:**
- If on a feature branch: analyze branch commits vs main
- If on main: analyze the last 5 commits
- If the user provides a different scope, use that

## Phase 2: Gather Changes

1. Run `git log` with the determined scope to get the commit list and messages
2. Run `git diff` for the full diff of the scope
3. If the diff is large (>500 lines), use `git diff --stat` first, then selectively read the top 3-5 most-changed files
4. **Read commit messages carefully** -- they contain intent that raw diffs miss
5. Only read changed files. Do not read the entire repo.

## Phase 3: Analyze

Identify the **dominant pattern** -- the single most instructive thing about these changes.

The rest: https://github.com/softaworks/agent-toolkit/blob/HEAD/dist/plugins/lesson-learned/skills/lesson-learned/SKILL.md